Multicellular Animals Emerged When Earth’s Magnetic Field Collapsed Billions Of Years Before

A fascinating new discovery offers “tantalizing” evidence for the origin of multicellular development on Earth. This groundbreaking find appears to be linked to a very rare event: a near-total collapse of the Earth’s magnetic field.

Approximately 650 million years ago, the Earth was relatively uneventful. However, shortly after, multicellular life began to emerge and diversify during the Ediacaran period. This emergence occurred within a 26 million-year window when the Earth’s magnetic field plummeted to one-thirtieth of its current strength.

Researchers from the University of Rochester have pointed out that this drastic reduction in the magnetic field would have led to a rapid decrease in hydrogen content in the Earth’s atmosphere and a corresponding increase in the oxidization of the air and oceans. These changes would have allowed for metabolically demanding activities, such as movement and propulsion, to become increasingly possible.

The Ediacaran Period, which lasted from 635 to 565 million years ago, provides the oldest confirmed fossil evidence of multicellular life on Earth. The organisms from this time were both diverse and complex for their era but extremely primitive compared to those in other epochs. These early life forms included tubular and frond-shaped creatures and some that had developed locomotion, such as the earliest jellyfish.

The Earth’s magnetic field, generated by its molten iron core, is essential for life. Beyond enabling compasses to function and creating the Aurora Borealis, the magnetic field protects the planet from solar wind, streams of radiation emanating from the Sun.

“Oxygen has long been identified as a key ‘environmental gatekeeper,’ allowing for evolutionary innovation and for meeting the energy demands of animals,” the researchers wrote. “Although sponges and microscopic animals can survive at low levels of dissolved oxygen, macroscopic, morphologically complex, and mobile animals require a greater amount of oxygen to support their metabolic demands.”

A weakened magnetic field would permit the Sun’s radiation to strip away lighter molecules like hydrogen from the Earth’s atmosphere. Hydrogen can escape into space through non-thermal processes as well. This could have resulted in an increase in oxygen levels sufficient to allow early macroscopic life to evolve in the oceans.

Study author Professor John Tarduno and his colleagues described the link between the earliest complex life forms and the magnetic field’s decline, which they uncovered through the study of plagioclase crystals that record magnetic signatures exceptionally well, as “tantalizing but unclear.” They noted that the oxygen content in samples from the Ediacaran period is significantly higher than in those from previous periods.

The team had previously discovered that the geomagnetic field recovered during the subsequent Cambrian Period, when most animal groups began to appear in the fossil record. This recovery of the protective magnetic field allowed life to thrive. “If the extraordinarily weak field had remained after the Ediacaran, Earth might look very different from the water-rich planet it is today: water loss might have gradually dried Earth,” Tarduno explained to Rochester University press.

This discovery sheds light on a critical period in Earth’s history, highlighting the interplay between the planet’s magnetic field and the development of early multicellular life. It provides a new perspective on the environmental factors that may have driven the evolution of complex life forms on Earth.